feat(prometheus): serialize resource as target_info gauge

[pichlermarc]

Which problem is this PR solving?

This PR updates the PrometheusExporter to export Resource as a gauge-typed target_info metric according to the specification here.

• When serializing resources, service.name and service.namespace are dropped from the resource attributes and used to construct the job label.
  • If job is already present in the resource, it is dropped instead.
• When serializing resources service.instance.id is dropped from the resource attributes, and its contents are added to the instance label.
  • If job is already present in the resource, it is dropped instead.

Fixes #867

Short description of the changes

Export Resource as a single gauge-typed target_info metric.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Added Unit tests
• Adapted existing tests.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #3300 (ea81f11) into main (92f2359) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3300   +/-   ##
=======================================
  Coverage   93.04%   93.05%           
=======================================
  Files         226      226           
  Lines        6517     6522    +5     
  Branches     1360     1360           
=======================================
+ Hits         6064     6069    +5     
  Misses        453      453           

Impacted Files	Coverage Δ
...etry-exporter-prometheus/src/PrometheusExporter.ts	92.00% <100.00%> (-0.41%)	⬇️
...ry-exporter-prometheus/src/PrometheusSerializer.ts	95.65% <100.00%> (+0.30%)	⬆️

[dyladan]

I think the lint failure was intermittent